43 
In the Crossopterygii ( “fringe-finned 55 Ganoids) the teeth 
are of remarkable structure, having a tree-like grouping of 
the dentine tubules, seen in cross section, hence the name 
“ Dendrodus ” for the teeth of Holoptychius. 
The Ganoids, or enamelled scale fishes, were either of the 
grovelling type (short and deep bodied), or predatory (with 
thinner and lithe bodies). The former are represented by 
Lepidotus and the latter by Caturus. Many of the short 
forms had bean-shaped teeth, which were shed successionally. 
Early types of Bony Eishes (Teleostei) are seen in Leptolepis 
and Osmeroides. Herrings (Clupea) made their appearance 
in the Cretaceous, and most of the living genera followed 
in early Tertiary times, as Pike, Perch, and Mackerel, of which 
there are examples shown here. 
The first Sharks were small and spiny, and began to appear 
in the Lower Devonian (Mesacanthus and Diplacanthus). 
The modern genera, as Lamna, did not exist, however, before 
Cretaceous times, whilst Carcharodon is typically early 
Tertiary to Recent, though some teeth have lately occurred 
in New Zealand rocks which have been referred to the 
Danian (Upper Cretaceous). 
Arthropoda. 
A good series of the animals with “ jointed feet 55 is shown 
here, including Flies (Diptera), Ants (Hymenoptera), Beetles 
Fig. 44. A Dipterous Insect — Protomyia buclclandi Heer. 
From the Oligocene of Aix, Provence, Southern France. 
